The Self-assembly And Regulation Of Supramolecular Chirality Based On The Amphiphilic Glutamide Cyano-stilbene

Supramolecular chirality refers to the molecule without chirality can produce CD signals under certain conditions or make the original chirality enhance under certain conditions through the weak interaction force of non-covalent bond.Supramolecular chirality originates from asymmetric stacking of chiral molecules or even achiral molecules,it contributes to a deeper understanding of the origin of living organisms and has important applications in asymmetric catalysis and advanced chiral materials.The methods to control supramolecular chirality include solvent,temperature,ultrasound,redox and acid base.In order to enhance the intermolecular forces,π-groups are often covalently attached to the assembly because they can provideπ-πpacking.Cyano-stilbene is a typical fluorescent group with aggregation-induced emission enhancement（AIEE）properties,which can achieve emission enhancement in the aggregation state,and cyano-stilbene based derivatives are easy to obtain,and attach different functional groups,it can show different molecular stacking patterns and the ability to response the external stimuli,so it is widely used in luminescent materials,biological probes,anti-counterfeiting materials and other research areas.In this paper,the amino acid glutamic acid is as the chiral center,cyano-stilbene and glutamic acid are covalently linked to obtain amphiphilic molecules,we explore its assembly ability and supramolecular chirality,and through the solvent,acid and base and other external stimuli to regulate the supramolecular chirality.Specific research contents are as follows:1)Amphiphilic molecules（GCS）containing long alkyl chains with cyano-stilbene as fluorescence group and glutamic acid as chiral center were designed and synthesized.It was found that GCS can form supramolecular gels in different solvents.It was found that L-GCS in toluene,a non-polar solvent,had a positive Cotton effect in CD spectra（from long wavelength to short wavelength）and a positive signal in CPL spectra,while L-GCS had a negative Cotton effect in CD spectra in polar solvent DMF/H₂O（f_w=40%）and a negative signals in CPL spectra.Therefore,supramolecular chirality can be regulated by adjusting solvent polarity and water fraction.In addition,GCS supramolecular gels can show signal switching properties by removing the solvent.This work provides new methods and insights for the preparation of intelligent response materials.2)The GCS molecules synthesized in Chapter 2 were doped with two organic dyes DBT（4,7-bis（2-thiophenyl）-2,1,3-benzothiadiazole）and BPEA（9,10-diphenylacetylidene anthracene）to form a two-component gel.It was found that the emission spectrum of GCS molecules overlaps with the absorption spectrum of DBT/BPEA by UV-vis and fluorescence tests,which can effectively carry out energy transfer.It was found that the energy transfer efficiency can be improved by increasing the polarity of solvent.In addition,when the molar ratio of donor GCS to acceptor DBT was 150/1,white emission supramolecular gels can be prepared in polar solvent acetonitrile.This study provides a new idea for improving energy transfer efficiency and preparing white emission materials.3)Amphiphilic molecules（GPCS）with pyridine-cyano-stilbene as fluorescent group and glutamic acid as chiral center were designed and synthesized.GPCS can form supramolecular gels at DMF/H₂O（f_w=40%）.After adding trifluoroacetic acid,it is found that the hydrogen on pyridine had a chemical shift to the low field in NMR spectra,and the chemical shift reached its maximum at 20 equivalent.After pyridine was protonated,the GPCS molecules still formed the structure of supramolecular gel.The CD signal of L-GPCS in DMF/H₂O（f_w=40%）showed a negative Cotton effect（from long wavelength to short wavelength）.With the increase of the amount of trifluoroacetic acid,the CD signal was weakened and reversed gradually.When the amount of trifluoroacetic acid reached 20equivalent,the Cotton effect showed a positive effect.At the same time,due to the protonation of pyridine,the transition energy level was reduced,and the fluorescence of GPCS molecule changes from cyan to yellow fluorescence.By adding trifluoroacetic acid,GPCS molecules can realize the dual conversion of fluorescence and chirality,which provides a new method for the construction of smart optical materials and chiral materials.